There are a number of ways to kill a process if you know the name of the process.
Here’s a couple different ways you can accomplish this. 
We are going to assume that the process we are trying to kill is named irssi
	
kill $(pgrep irssi)
 
killall -v irssi
 
pkill irssi
 
kill `ps -ef | grep irssi | grep -v grep | awk ‘{print $2}’` 


These techniques can be useful in shell scripts, 
where you wouldn’t know the process ID and would 
need to restart or kill a process.